Method for producing thread bundle derived from bagworm silk threads spun on the surface of a base material

ABSTRACT

A bagworm silk thread spun on a base material was conventionally difficult to be collected, and thus, cannot be utilized. An object of the present invention is to develop and provide a method in which such a bagworm silk thread is peeled off from a base material with a weak force without being damaged and is collected as a thread bundle.Provided is a method for producing a thread bundle of a bagworm silk thread, including: applying, to a bagworm silk thread spun on the surface of a base material, a wetting liquid which presents a liquid form at least in the range of 20° C. or more and less than 30° C. and does not damage, denature, or dissolve the silk thread; and then separating the bagworm silk thread from the base material.

TECHNICAL FIELD

The present invention relates to a method for producing a thread bundleconsisting of foothold silk thread obtained by allowing a bagworm tospin the foothold silk thread onto the surface of a base material.

BACKGROUND ART

The thread consisting of an insect cocoon or a hair of mammal has beenused as an animal fiber for a clothes and the like since long time ago.Especially, silk thread from a silk moth (Bombyx mori) larva, namely asilkworm, which is herein often referred to as “silkworm silk thread”,has excellent properties for absorption and desorption of moisture,moisture retention, and heat retention, and also has a unique gloss anda smooth texture. Therefore, the silkworm silk thread is valuable andexpensive natural material even today.

However, there exist animal fibers in nature having propertiescomparable or superior to those of silkworm silk thread. Recently, forutilizing an animal fiber having such excellent properties as novelnatural material, exploration thereof and research and developmentthereon are ongoing.

A thread from a spider (herein often referred to as “spider thread”) isone material of interest. A spider thread has flexibility and elasticityand has an elastic force up to 5 to 6 times greater than that ofpolystyrene, and is thus expected to be used as a medical material forsurgical suture, for example, and as a special material for emergencyropes, protective clothes, or the like (Non-Patent Literatures 1 and 2).However, mass-production of spider threads is not feasible because massrearing of spiders and collecting a large amount of thread from spidersare difficult, which also results in a problem of high production cost.An attempt to solve this problem is ongoing by using gene recombinationtechnology to produce a spider thread in a host such as a silkworm orEscherichia coli (Patent Literature 1 and Non-Patent Literature 2).However, a silkworm or Escherichia coli for spider thread production isa recombinant and is thus allowed to be reared or cultured only infacilities with predetermined equipment, which poses a problem of largemaintenance or management burden. Additionally, a liquid spider threadprotein expressed in Escherichia coli needs to be converted to a fiber,which also causes a problem in that the number of processes increasesaccordingly. Furthermore, another problem is that the current spiderthread spun by a recombinant silkworm is merely comprised in silkwormsilk thread at several percentages and cannot be obtained as 100% spiderthread which allows 100% of the properties of spider thread to beutilized.

There exists an insect called a bagworm (alias “basket worm”). Thelarvae of moth belonging to the family Psychidae in the orderLepidoptera is collectively referred to as a bagworm and is known tospend the whole larval stages living with a spindle-shaped orcylinder-shaped nest made of pieces of leaves and twigs assembled bythread, as shown in FIG. 1A, during which the larva usually hide itselfinside the nest and move with the nest even for eating.

The silk thread spun by the bagworm (herein often referred to as“bagworm silk thread”) has recently been attracting attention as a newanimal-fibrous natural material having more excellent properties thanthe silkworm silk thread and the spider thread. For example, the bagwormsilk thread from the bagworm Eumeta minuscula has an elastic modulus upto 3.5 times of that of the silkworm silk thread and up to 2.5 times ofthat of the Nephila clavata spider thread, and a very high strength(Non-Patent Literatures 1 and 2). Additionally, the bagworm silk threadnot only have a gloss and a shiny appearance comparable or superior tothose of the silkworm silk thread but also allow production of muchfine, thin and light fabric with a smooth texture compared to thesilkworm silk thread because monofiber of the bagworm silk thread has across-sectional area only about one-seventh of that of the silkworm silkthread.

The bagworm is more advantageous than the silkworm and the spider alsoin terms of rearing. The bagworm is phytophagous, as is the silkworm.Thus, differently from the spider, which is carnivorous, the bagwormfood is easy to procure and can be supplied stably. Additionally, thebagworm is phytophagous similarly to but more advantageously than thesilkworm. For example, since the silkworm feeds on only raw leaves ofmulberry (species belonging to the genus Morus, comprising, for example,M. bombycis, M. alba, and M. Ihou) in principle, the region for rearingand season for rearing depend on the supply area of mulberry leaves andthe season of mulberry leaf development. In contrast, the bagworm iseuryphagous, the specificity for food leaves is low, and many species ofthe bagworm can feed on leaves of trees of various species. Accordingly,food leaves for the bagworm are easily available, and the bagworm can beraised in any region. Also, the bagworm of some species can feed onleaves of evergreen trees. Thus, differently from mulberries, which aredeciduous trees, it is possible to supply food leaves all year round.Moreover, the bagworm is smaller in size than the silkworm and requiresa rearing space equal to or less than that required for rearing thesilkworm, which makes mass rearing easy. Thus, the cost for rearing canbe reduced.

Also, the bagworm is superior to the silkworm in terms of productivity.For example, the silkworm spins a large amount of thread only duringcocooning and all larvae perform cocooning in the same period. Thus,thread collection periods overlap and labor periods concentrate thereon.However, the bagworms repeatedly spin silk thread for nest building ormigrating throughout larval stages. Thus, labor periods can be dispersedby artificially adjusting the thread collection periods.

As described above, the bagworm silk thread has properties superior tothose of the silkworm silk thread and the spider thread, and also hasmany advantages for their production, and thus, is expected as a verypromising novel natural material.

However, the bagworm silk thread has several problems in the practicalapplication thereof. One of them is a problem associated with thecharacteristics of the bagworm nest. Contaminants, such as pieces ofleaves and twigs, are inevitably attached on the surface of the bagwormnest. This is due to the habit of the bagworm incorporating small piecesof twigs and leaves into the nests from the surroundings for camouflagein the process of nest production and expansion. These contaminants needto be completely removed for commercialization of the bagworm silkthread. In conventional method, these contaminants are manually removedfrom the built nest, or are detached from the nest after the nest isimmersed in warm water for a long time to be softened. However, the workof removing these contaminants requires enormous labor. Additionally,complete removal of the contaminants is not possible with existingtechnologies, resulting in a problem in that only low quality finalproducts can be obtained, due to contamination with a small amount ofsmall pieces of leaves and the like, as well as light-brown staining ofthe bagworm silk thread with pigments from the contaminants and so on.Decolorization treatment can be performed using a base or an acid toremove the pigments, but can result in a marked decrease in quality suchas an impaired strength of the bagworm silk thread.

The bagworm silk thread comprises a silk thread called a foothold silkthread, as well as a nest silk thread constituting the nest. As shown inFIG. 1B, this foothold silk thread is a silk thread spun to be used as ascaffold for preventing the bagworm from falling when the bagwormmigrates. The results of the present inventors' studies have revealedthat this foothold silk thread is tougher and has excellent mechanicalproperties than the nest silk thread. Additionally, the foothold silkthread has no contaminant such as pieces of leaves and twigs,differently from the nest silk thread. Accordingly, if the footholdthread can be collected to be utilized, it can serve as a practicalbagworm silk thread.

However, such a method still has a problem. First, foothold thread isusually spun in the intended direction and in a zigzag pattern, as shownin FIG. 2A. The bagworm silk thread is spun in the form of a mixture ofa fiber component and a paste-like protein covering the surface thereof,and in the case of the foothold silk thread, the foothold silk thread isfixed to the surface of a base material by the paste-like protein (asshown by the arrowheads in the larger circle in FIG. 2A) at theturnaround points in the zigzag pattern. This fixation is very strong,and thus, a strong tension is necessary to mechanically peel thefoothold silk thread from the base material. In many cases, such anoperation also causes the foothold silk thread to be broken around thefixed portion and to be fragmented. Furthermore, the migration of abagworm is generally difficult to control, and it is possible that abagworm migrates among the same place back and forth for number oftimes. As a result, the silk threads spun in a zigzag pattern overlapand entwine one another in the form of a complicated entanglement asshown in FIG. 2B that it is even more difficult to collect the silkthread from the base material without damaging the thread. For thisreason, foothold silk thread spun on a base material has hitherto neverbeen utilized effectively as a natural fiber material.

CITATION LIST Patent Literature

-   Patent Literature 1: WO2012/165477

Non-Patent Literature

-   Non-Patent Literature 1: Shigeyosi Ohsaki, 2002, Sen'i Gakkaishi    (Sen'i To Kogyo), 58: 74-78.-   Non-Patent Literature 2: Kuwana Y, et al., 2014, PLoS One, DOI:    10.1371/journal.pone.0105325

SUMMARY OF INVENTION Technical Problem

A bagworm foothold silk thread spun on a base material is conventionallydifficult to be collected and cannot be utilized. A purpose of thepresent invention is to develop and provide a method in which such abagworm foothold silk thread can be peeled from a base material with aweak force without being damaged and can be collected as a thread bundleso as to be utilized.

Solution to Problem

To solve the above-mentioned problems, the present inventors havevigorously made studies, and as a result, have succeeded in enabling abagworm silk thread spun on a base material to be peeled in the form ofa thread bundle from the base material without being damaged, by such abagworm silk thread is sprayed or coated with a wetting liquid such asethanol, an aqueous solution, or an organic solvent and peeled with aforce of only 15% or less, compared with a negative control with such awetting liquid not being used. The present invention provides thefollowings based on the method described above.

(1) A method for producing a thread bundle of a bagworm silk thread(s),comprising: wetting liquid applying process of applying a wetting liquidto the bagworm silk thread(s) spun on the surface of a base material;and

separation process of separating the bagworm silk thread(s) from thebase material,

wherein the wetting liquid presents a liquid form at least in the rangeof 20° C. or more and less than 30° C. under the atmospheric pressure,and is a pure substance or a mixture that does not damage, denature, ordissolve a fibroin protein which is a fiber component of the bagwormsilk thread(s).

(2) The method according to (1), comprising a spinning process ofplacing a bagworm on the surface of the base material before the wettingliquid applying process and allowing the bagworm to spin the thread.

(3) The method according to (2), further comprising a bagworm collectionprocess of collecting the bagworm together with a nest after thespinning process and before the wetting liquid applying process.

(4) The method according to any one of (1) to (3), comprising a washingprocess of washing the separated bagworm silk thread(s).

(5) The method according to any one of (1) to (4), comprising adegumming process of degumming the separated bagworm silk thread(s).

(6) The method according to any one of (1) to (5), wherein the wettingliquid is a pure substance or a mixture that has a melting point of lessthan 20° C. and a boiling point of 30° C. or more and 300° C. or less.

(7) The method according to any one of (1) to (6), wherein the wettingliquid is an aqueous solution or an organic solvent.

(8) A method for collecting a bagworm silk thread(s) spun on the surfaceof a base material, comprising:

wetting liquid applying process of applying a wetting liquid to thebagworm silk thread(s) spun on the surface of the base material; and

separation process of separating the bagworm silk thread(s) from thebase material,

wherein the wetting liquid presents a liquid form at least in the rangeof 20° C. or more and less than 30° C. under the atmospheric pressure,and is a pure substance or a mixture that does not damage, denature, ordissolve a fibroin protein which is a fiber component of the bagwormsilk thread(s).

(9) The method according to (8), wherein the wetting liquid is anaqueous solution or an organic solvent.

(10) A bagworm silk thread(s) obtainable by using the method forproducing a thread bundle according to any one of (1) to (7) or themethod for collecting a bagworm silk thread(s) according to (8) or (9).

(11) An unwoven fabric formed of a bagworm silk thread(s) obtainable byusing the method for producing a thread bundle according to any one of(1) to (7).

The present specification encompasses the contents disclosed in thespecification and/or drawings of Japanese Patent Application No.2018-158762, on which the priority of the present application is based.

Advantageous Effects of Invention

The method for producing a thread bundle of a bagworm silk threadaccording to the present invention makes it possible that a bagwormfoothold thread spun on the surface of a base material, which wasconventionally difficult to be collected, is collected with a weak forcewithout being fragmented.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A shows the appearance of a nest of a bagworm of Eumeta japonica(Eumeta japonica bagworm). FIG. 1B shows the spinning behavior of aEumeta japonica bagworm in migration. This shows how the bagworm moveswhile spinning a foothold silk thread (as shown by the arrowhead) andhooks its claws onto the spun bagworm silk thread (foothold silk thread)(as shown by the thin arrows).

FIG. 2A is a schematic diagram showing the spun state of the bagwormsilk thread (foothold silk thread) spun by a bagworm migrating on thesurface of a base material. As shown here, the bagworm foothold silkthread presents a ladder-like zigzag pattern. In the figure, the blackarrows indicate the direction in which the bagworm migrates spinning thethread. Additionally, the view in the larger circle is an enlarged viewof that in the smaller circle, and the arrowheads in the larger circleindicate a paste-like protein. The foothold silk thread is fixed on thebase material at the turnaround points of the zigzag portionscorresponding to the steps of the ladder. FIG. 2B shows the state of thebagworm silk thread, which is a thread spun on a plastic plate by theEumeta japonica bagworm. This shows how the bagworm silk threads spun ina zigzag pattern are entangled complicatedly.

FIG. 3 shows a process flow diagram of a method for producing a threadbundle of a bagworm silk thread according to the present invention.

FIG. 4 is the graphs showing the results of a peeling tension evaluationtest performed in Example 1. In the graphs, (A), (B), and (C) show thetest results of a negative control with no wetting liquid appliedthereto, a sample with water applied thereto, and a sample with ethanol(99.5%) applied thereto respectively.

DESCRIPTION OF EMBODIMENTS

1. Method for Producing Thread Bundle of Bagworm Silk Thread

1-1. Concept

The first aspect of the present invention is a method for producing athread bundle of a bagworm silk thread. The production method accordingto the present invention is a method in which a thread bundle consistingof an intended bagworm silk thread is obtained by applying a wettingliquid to a bagworm silk thread spun on the surface of a base materialand then separating the bagworm silk thread from the base material. Themethod according to the present invention makes it possible that afoothold silk thread, which has excellent properties but is difficult tocollect without being physically damaged and thus, has never beenutilized, is efficiently collected without being damaged.

1-2. Definition of Terms

The following terms frequently used herein are defined as describedbelow.

The term “bagworm” collectively refers to a moth larva belonging to thefamily Psychidae in the order Lepidoptera, as described above. Mothsbelonging to the family Psychidae are distributed worldwide and thelarva (bagworm) of any species of the moth spends the whole larvalstages living in a nest covered with natural materials, such as piecesof leaves and twigs, which are assembled by silk threads spun by thelarva itself. Additionally, any species of bagworm has the habit ofspinning a foothold silk thread which functions as a scaffold in theintended direction of migration to prevent the bagworm from falling whenthe bagworm migrates. Accordingly, the species, instar, and gender ofbagworms used herein are not limited, as long as that the bagworm is alarva of a moth species belonging to the family Psychidae and that thespecies has the habit as described above. For example, the familyPsychidae comprises the genera Acanthopsyche, Anatolopsyche, Bacotia,Bambalina, Canephora, Chalioides, Dahlica, Diplodoma, Eumeta, Eumasia,Kozhantshikovia, Mahasena, Nipponopsyche, Paranarychia, Proutia, Psyche,Pteroma, Siederia, Striglocyrbasia, Taleporia, Theriodopteryx,Trigonodoma, etc., and the bagworm used herein may be a speciesbelonging to any genus. Additionally, the instar of the larva may be anyinstar between the first instar and the last instar. However, a largerbagworm is preferable to obtain a large mass of the bagworm silk thread.For example, among larvae of the same species, a larva in the lastinstar is more preferable, and a female larva is more preferable than amale larva because the female grows larger than the male. Furthermore,among the family Psychidae, a large species is more preferable. Forexample, Eumeta japonica and Eumeta minuscula, which are large species,are suitable as species used in the present invention.

A bagworm to be used in a method for producing according to the presentinvention is preferably, but is not limited to, a bagworm keeping anest. “Keeping a nest” refers to the state in which the bagworm has anest therewith. As described above, the bagworm lives with its own nest,and exposes only part thereof out of the nest even during eating andmoving, as shown in FIG. 1B, and in principle, the bagworm never exposesits whole body out of the nest throughout the whole larval stage. Whenthe bagworm is artificially separated from the nest and wholly exposedto the outside, the bagworm thus made naked generally minimizes itsmovement and promptly starts rebuilding a nest for self-protection andto keep itself warm. Accordingly, the reason why a bagworm keeping anest is suitable is not to make prioritize the behavior of spinning anest silk thread but rather to make actively spin a foothold silkthread, which is a purpose of the present invention.

The term “silk thread” as used herein refers to a thread derived from aninsect and made of proteins, which is spun by the insect in a larval oradult stage for the purpose of nest building, migrating, anchoring,cocooning, prey capture, and the like. When the term “silk thread” issimply recited herein, it refers to a general silk thread from anunspecified insect. In case of indicating a silk thread from aparticular insect species, the name of the organism is placed before theterm “silk thread,” as a “silkworm silk thread” or a “bagworm silkthread.”

The term “bagworm silk thread” as used herein refers to a silk threadspun by a bagworm. The “bagworm silk thread” herein encompasses amonofiber, spun fiber, and fiber assembly. The term “monofiber”, whichis also referred to as monofilament, is the smallest filament unitconstituting fiber components. The monofiber contains a fibroin proteinas a main component. The bagworm silk thread and the silkworm silkthread in natural states are spun in the form of bifilament in which twomonofibers are joined together by a sericin protein, a gummy material.This bifilament is referred to as a “spun fiber”. The bagworm nest andthe silkworm cocoon are constituted with spun fiber(s). Also, a fiberbundle formed by assembling plural spun fibers is referred to as a“fiber assembly (or multifilament)”. In general, this fiber assemblycorresponds to a raw silk thread. Furthermore, silk thread obtained bytreatment of raw silk thread with an enzyme and a basic chemical such assoap, lye, sodium carbonate, and urea to remove sericin protein iscalled degummed silk thread.

The bagworm silk thread includes two kinds of the silk thread: footholdsilk thread and nest silk thread. As described above, the “foothold silkthread” refers to a silk thread spun by a bagworm for the purpose of itsmigration, which has a function as a foothold (scaffold) for preventingit from falling from a branch, a leaf, or the like. On the other hand,the “nest silk thread” refers to a bagworm silk thread spun for forminga nest, which is spun to assemble pieces of leaves and twigs or to makean internal wall of a nest so that its accommodation space becomes acomfortable environment. A foothold silk thread is intended as a bagwormsilk thread in the present invention in view of the purpose. Thus, theexpression “bagworm silk thread” herein refers to a foothold silk threadunless otherwise specified.

As used herein, a “thread bundle” refers to a silk thread aggregateconsisting of a bagworm foothold silk thread(s) alone. A bagworm nest isan aggregate of a bagworm silk thread(s), but usually is a mixture ofcontaminants of small pieces of twigs, leaves, and the like, and isconsisting of a nest silk thread(s). Therefore, it is not the threadbundle according to the present invention. The thread bundle herein is,but is not limited, an aggregate of a foothold silk thread(s) with nocontaminant intruded produced through some artificial process. Examplesof such thread bundles comprise a thread bundle which a bagworm placedon a base material is allowed to spin. Without limitation, the state ofthe thread bundle may be, for example, a sheet-like state such as anunwoven fabric in which one or more bagworm silk threads are entwinedcomplicatedly, or may be an assembled state in which one or more bagwormsilk threads are reelably held together.

A “wetting liquid” refers to a pure substance or a mixture whichpresents a liquid form at least in the range of 20° C. or more and lessthan 30° C. under the atmospheric pressure, and does not damage,denature, or dissolve a fibroin protein which is a fiber component ofthe bagworm silk thread. Accordingly, a pure substance which is in astate other than a liquid state in the above-mentioned temperaturerange, and a substance in a liquid state which denatures a proteinincluding a strongly acid solvent, a strongly basic solvent, a mixturesuch as a solution containing protease, or the like are not suitable asa wetting liquid in the present invention.

A “pure substance” refers to a chemical substance having certainproperties, and examples thereof comprise a simple substance consistingof a single element, and a compound consisting of a plurality ofelements. A pure substance in the present invention usually corresponds,but is not limited, to a compound.

A “mixture” refers to a substance formed by mixing a plurality of puresubstances. A mixture corresponds to, for example, a solution.

A wetting liquid may be consisting of any pure substance or a mixture aslong as the wetting liquid satisfies the above-mentioned requirements.Examples thereof comprise, but are not limited to, compounds having amelting point (Melting Point: MP) of less than 20° C. and a boilingpoint (Boiling Point: BP) of 30° C. or more and 300° C. or less undernormal temperature (25° C.) and normal pressure (100 kPa). A compoundhaving such properties often has the properties as a “solvent” which candissolve another compound as a solute.

Specific of a compound for wetting liquids are as mentioned below, but awetting liquid herein is not limited to the examples below.

A wetting liquid may be a liquid consisting of a polar molecule (polarsolvent). Examples thereof comprise: protic polar solvents such as water(MP: 0° C.; BP: 100° C.), methanol (MP: −96° C.; BP: 64.7° C.), ethanol(MP: −117° C.; BP: 78.3° C.), 1-propanol (MP: −127° C.; BP: 97.2° C.),1-butanol (MP: −90° C.; BP: 118° C.), glycerin (MP: 17.8° C.; BP: 290°C.), formic acid (MP: 8.3° C.; BP: 100.8° C.), acetic acid (MP: 15° C.;BP: 118° C.), and butyric acid (MP: −7.9° C.; BP: 164° C.); and aproticpolar solvents such as DMSO (MP: 18.5° C.; BP: 189° C.), acetonitrile(MP: −48° C.; BP: 81.6° C.), acetone (MP: −94° C.; BP: 56° C.),dimethylformamide (MP: −61° C.; BP: 153° C.), dimethylsulfoxide (MP: 19°C.; BP: 189° C.), tetrahydrofuran (MP: −108° C.; BP: 66° C.), and1,1,1,3,3,3-hexafluoro-2-propanol (MP:−3.3° C.; BP:58.2° C.). Otherexamples comprise an ionic liquid. Here, the values in the parenthesisfollowing each compound indicate a melting point (MP) and a boilingpoint (BP) under normal temperature and normal pressure (the sameapplies hereinafter).

A wetting liquid may also be a nonpolar liquid consisting of a nonpolarmolecule (nonpolar liquid: nonpolar solvent). Examples thereof comprisean oil and many organic solvents (low polarity organic solvents)excluding some. An oil is a compound in a liquid state under normaltemperature and normal pressure, and examples thereof comprise a fattyacid represented by the general formula: R—COOH (wherein R is a C₄₋₈alkyl group). Specific examples of nonpolar liquids comprise: fattyacids such as valeric acid (valerianic acid: MP: −34.5° C.; BP: 186°C.), caproic acid (hexanoic acid: MP: −3° C.; BP: 205° C.), enanthicacid (heptylic acid, heptanoic acid: MP: −7.5° C.; BP: 223° C.),caprylic acid (octanoic acid: MP: 16.7° C.; BP: 239.7° C.), pelargonicacid (nonanoic acid: MP: 11° C.; BP: 247° C.), palmitoleic acid(hexadecenoic acid: MP: −0.1° C.; BP: 230° C.), linoleic acid(octadecadienoic acid: MP: −5° C.; BP: 229° C.), linolenic acid(octadecatrienoic acid: MP: −11° C.; BP: 278° C.), and arachidonic acid(eicosatetraenoic acid: MP: −49° C.; BP: 169° C.); hexane (MP: −95.3°C.; BP: 68.7° C.); toluene (MP: −95° C.; BP: 110.6° C.); chloroform (MP:−63.5° C.; BP: 61° C.); dichloromethane (MP: −95° C.; BP: 39.8° C.);1,2-dichloroethane (MP: −35.7° C.; BP: 83.4° C.); trichloroethylene (MP:−86.4° C.; BP: 87° C.); acetone (MP: −94° C.; BP: 56° C.); diethyl ether(MP: −116° C.; BP: 34.6° C.); xylene (MP: −25° C.; BP: 137° C.); carbontetrachloride (MP: −23° C.; BP: 76.7° C.); methyl acetate (MP: −98° C.;BP: 57° C.); and ethyl acetate (MP: −84° C.; BP: 77° C.).

Additionally, in cases where a wetting liquid herein is a mixture,specific examples thereof comprise a solution. Examples of suchsolutions comprise, but are not limited to: a solution consisting of apolar liquid or nonpolar liquid in which one or more different solutesare dissolved; a colloidal solution or sol in which a colloid isdispersed in a liquid which is a dispersion medium; two or moredifferent liquids (for example, a liquid mixture or the like consistingof different polar liquids); or a combination thereof. Examples of polarsolutions comprise: an aqueous solution in which a solute is dissolvedin water; and a solution mixture of solvents such as of ethanol andwater. Solute in the aqueous solution is not limited. Examples thereofcomprise, but are not limited to, a salt, a sugar, and a surfactant. Apreferable salt is, but is not limited to, a salt having highsolubility. Examples thereof comprise sodium chloride salt, potassiumchloride salt, sodium carbonate salt, and sodium hydrogencarbonate salt.The solute concentration of the solution is not particularly limited.For example, it may be equal to solubility. Solute concentration for thesolution mixture is also not limited in particular. For example, aliquid mixture of ethanol and water may be 10%, 20%, 30%, 40%, 50%, 60%,70%, 80%, 90%, 95%, or 99.5% ethanol.

As mentioned above, a pure substance or mixture constituting a wettingliquid is not limited to any type. Considering the easiness of handling(including waste liquid disposal), safety, and purchasing cost, water(including warm water and hot water), an aqueous solution, ethanol, anda liquid mixture thereof are preferable; and an aqueous solution andethanol are particularly preferable.

As used herein, a “base material” refers to a base for collecting abagworm silk thread. A bagworm placed on the surface of this basematerial is allowed to migrate, thus spinning a bagworm silk thread onthe surface.

A material constituting a base material is not limited as long as it canfix a bagworm silk thread on its surface with a paste-like protein.Examples thereof comprise glass (comprising enamel), metal, a syntheticresin (comprising a thermoplastic resin, a thermosetting resin, and asynthetic rubber), ceramic, paper, a piece of plant (comprising, forexample, a piece of wood), or a piece of animal (comprising, forexample, a piece of bone, seashell, and sponge). However, a basematerial which is dissolved by a wetting liquid used or causes areaction such as an oxidation-reduction reaction with a wetting liquiddoes not fit with the spirit of the present invention in which a bagwormsilk thread spun on a base material is collected. Accordingly, amaterial constituting a base material is desirably a material insolublein and nonreactive with a wetting liquid used in the present invention.Being “insoluble in a wetting liquid” refers to the property of notbeing dissolved in a wetting liquid used in the present invention.Additionally, being “nonreactive with a wetting liquid” refers to theproperty of causing no chemical reaction with a wetting liquid used inthe present invention. Accordingly, the material of a base material inthe present invention can be vary depending on the type of the wettingliquid used. For example, with a wetting liquid such as water or anaqueous solution, a synthetic resin can be used, such as polyethylene,polypropylene, polystyrene, vinyl acetate, cellulose acetate, acrylicresin, or polycarbonate, but with a wetting liquid such as a lowpolarity organic solvent, those having solubility therein cannot beused, such as polystyrene, vinyl acetate, cellulose acetate, acrylicresin, polycarbonate, or the like. Glass, ceramic, polypropylene, or thelike, which is readily available and relatively inexpensive and has lowreactivity, is suitable as the material of a base material.

The thickness of a base material used in this process is not limited.The thickness can suitably be determined considering the production costand rigidity of the base material, the easiness of processing in thesubsequent processes, and the like. For example, it is preferable thatan average thickness of the base material is 0.5 mm or more, 0.6 mm ormore, 0.7 mm or more, 0.8 mm or more, 0.9 mm or more, 1.0 mm or more,1.2 mm or more, or 1.5 mm or more, and in addition, may be 3.0 mm orless, 2.8 mm or less, 2.5 mm or less, 2.2 mm or less, or 2.0 mm or less.In cases where the base material is consisting of a thin film having anaverage thickness of less than 0.5 mm, 0.4 mm, 0.3 mm, 0.2 mm, or 0.5mm, the base material itself does not have enough rigidity to retain agiven shape, and thus, the base material may be placed on a suitablesupport.

As used herein, a “support” refers to a member on the surface of which abase material is placed so that rigidity and/or a shape is given to thebase material. The support is an optional constituent to be used in themethod according to the present invention, and can be used if necessary.The material of the support is not particularly limited as long as ithas enough rigidity to retain a given shape. Examples thereof compriseglass, metal, plastic, synthetic rubber or ceramic, or paper, a piece ofplant or a piece of animal.

The shape and size of a base material used in this process are notlimited. For example, the shape may be a sheet-like or plate-like planarshape, or may be a three-dimensional shape, and is preferably a planarshape, considering the easiness of separating the base material from thebagworm silk thread. Additionally, the surface condition of basematerial is preferably, but is not limited to, smooth surface from whichbagworm silk thread can be easily separated rather than that which isrough surface to which the thread can be strongly fixed. The size of thebase material can be that which is selected as necessary, and in view ofthe fact that the foothold silk thread is a bagworm silk thread spunduring migration, the lower limit is preferably a size equal to orgreater than the size of the bagworm and the body length of the bagworm.For example, the long axis or the major axis can be 1 cm or more, 2 cmor more, 3 cm or more, 4 cm or more, or 5 cm or more. Additionally, thesize of the base material is not limited to any upper limit, but incases where the long axis or the major axis is 10 cm or more, 15 cm ormore, 20 cm or more, 25 cm or more, or 30 cm or more, it is morepreferable to allow a plurality of bagworms to spin threads.

1-3. Method

The process flow diagram of this aspect is shown in FIG. 3. As shown inthis Figure, the method according to the present aspect comprises: awetting liquid applying process (S0103) and a separation process (S0104)as essential processes; and a spinning process (S0101), a bagwormcollection process (S0102), a washing process (S0105), and a degummingprocess (S0106) as optional processes. Each of the processes will bedescribed below in flow order.

1-3-1. Spinning Process

The “spinning process” (S0101) is a process of placing a bagworm on thesurface of a base material or placing a bagworm together with a basematerial and allowing the bagworm to spin a thread. This process is anoptional process in the present invention. This process is performedbefore the wetting liquid applying process mentioned below.

“Placing a bagworm on the surface of a base material” refers topositioning both of them such that the bagworm can touch the surface ofthe base material. For example, the bagworm may be directly placed onthe arranged base material, or be placed so that the bagworm can migrateto reach the base material. Specific examples of the latter optioncomprise a case in which a bagworm is placed on the bottom of a lidlesswide-mouthed plastic container, and then, a base material is used as alid for the container. The bagworm prefers a higher position andaccordingly migrates along the inner sidewall of the wide-mouthedplastic container to reach the undersurface of the base materialcorresponding to the ceiling of the container, followed by spinning afoothold silk thread while migrating on the base material. Thearrangement of the base material on which a bagworm silk thread is spunis not particularly limited. As mentioned above, the base material maybe arranged on the ceiling of a container, or may be arranged on thewall thereof. It is convenient to arrange the base material on a portionother than the bottom as such because feces defecated by a bagworm fallon the bottom and the surface being spun on is not contaminated by thefeces.

In this regard, the species and the number of the bagworm to be placedare not limited. For example, one bagworm or a plurality of bagworms maybe placed at one time per base material onto which the bagworm silkthread is to be spun. Additionally, the species or age of the bagworm tobe placed are not limited. In cases where a plurality of bagworms areplaced, the individuals may be of the same species and the same age, ormay be a mixture of bagworms of different species or different ages.

The period of time for this process is not particularly limited. Theprocess period depends on species and age of the bagworm, and the numberof individuals to be used, but in any case, the process may usually becontinued until a necessary amount of thread is spun on a base material.For example, when one last instar bagworm of Eumeta japonica is used tospin a thread onto a circular base material having a diameter of 9 cm,the bagworm is allowed to spin for 1 day or more, 2 days or more, 3 daysor more, 4 days or more, 5 days or more, 6 days or more, or 7 days ormore. As described above, the bagworm foothold silk thread is spun whilethe bagworm migrates, and thus, the amount of the obtained silk threadis in proportion to the migration distance of the bagworm in principle.Therefore, by using a plurality of bagworms to spin, time of thespinning process is shorter than that by using a single bagworm to spin.In addition, the bagworm is not allowed to eat food while spinning, andthus, the bagworm often stops spinning in this process. In such a case,the bagworm may be exchanged for a new one to continuously maintain thespinning process.

It is recommended that the temperature and humidity in this process beconstant or with little change so that the amount of thread spun by abagworm per unit time can be larger. It is preferable that thetemperature is around 20° C., for example, ranges from 15° C. to 25° C.,or from 18° C. to 22° C., and that the humidity is around 50%, forexample, ranges from 40% to 65%, or from 45% to 60%. There is no limitabout light and dark period during this process, and it may have only alight period, or may have cyclical light and dark periods. For example,the cycle may be such that, in 24 hours, the light period is 6 hours to18 hours, 7 hours to 17 hours, 8 hours to 16 hours, 9 hours to 15 hours,10 hours to 14 hours, 11 hours to 13 hours, or 12 hours, and the rest isthe dark period.

1-3-2. Bagworm Collection Process

The “bagworm collection process” (S0102) is a process of collecting thebagworm used in the spinning process together with the nest, and is anoptional process in the present invention. A purpose of this process isto separate the bagworm no longer required from the base material andcollect it after the spinning process.

After the spinning process, the spun foothold silk thread and thebagworm which has spun the thread coexist on the base material. Inprinciple, however, the bagworm is not needed in the subsequent wettingliquid applying process. In addition, when the liquid to be used isapplied to a bagworm in the wetting liquid applying process, it ispossible that the bagworm silk thread is stained with an undesirablecolor by the bodily fluid of the bagworm and the extract from deadleaves and the like used for the nest. Thus, this process is an optionalprocess, but is preferably performed after the spinning process.

The method for collecting a bagworm from the base material is notlimited. Any method for separating a bagworm from the base material canbe utilized. For example, the bagworm in contact with the base materialmay be peeled away together with the nest. However, for purposes of thepresent invention, it is preferred that the damage to the bagworm silkthread is as low as possible. For example, the bagworm may be induced tospontaneously leave the base material. Specific examples of such amethod comprise a method in which, utilizing the feature of the bagworm,which migrates to a higher place, the container is turned upside down sothat the position of the base material can be changed from the ceilingto the bottom. After the bagworm migrates to the inner sidewall of thecontainer, the base material can be collected. Another method is heatingof the base material. The bagworm spontaneously leaves the base materialto escape from high temperature, and thus, the base material can becollected after the migration. The heating temperature may be ordinarytemperature or more and the temperature without the damage of thebagworm silk thread and melting the base material. For example, thetemperature may be 30° C. or more, 33° C. or more, 35° C. or more, 38°C. or more, 40° C. or more, 42° C. or more, 45° C. or more, 48° C. ormore, or 50° C. or more, and 80° C. or less, 75° C. or less, 70° C. orless, 65° C. or less, 60° C. or less, or 55° C. or less.

Incidentally, the collected bagworm can be fed and then reused in themethod for producing according to the present invention.

1-3-3. Wetting Liquid Applying Process

The “wetting liquid applying process” (S0103) is a process of applying awetting liquid to a bagworm silk thread spun on the surface of a basematerial, and is the most important essential process in the presentinvention.

The method for applying wetting liquid is not limited. Any method can beused as long as by which the bagworm silk thread on the surface of abase material is sufficiently wetted with a wetting liquid. For example,the method comprises a method for spraying, splashing, or spreading awetting liquid onto the surface of a base material having a bagworm silkthread spun thereon, and a method for immersing a base material having abagworm silk thread spun thereon in a wetting liquid.

After the wetting liquid is applied, it is preferably retained for apredetermined time. This is in order to ensure the time for the wettingliquid to sufficiently permeate between the base material and thebagworm silk threads. The length of the “predetermined time” herein isnot limited in particular. The time depends on the amount of a wettingliquid to be applied and the applying method, and usually may be from 1second to 1 hour, from 1 minute to 40 minutes, from 2 minutes to 30minutes, from 3 minutes to 20 minutes, from 4 minutes to 15 minutes, orfrom 5 minutes to 10 minutes, after the application.

The temperature of a wetting liquid used in this process is not limitedin particular as long as the temperature does not damage, denature, ordissolve the bagworm silk thread. The temperature is usually be in therange of room temperature, for example, from 1° C. to 35° C., from 5° C.to 32° C., from 10° C. to 30° C., from 12° C. to 27° C., from 15° C. to25° C., or from 18° C. to 20° C., when the wetting liquid has a meltingpoint of less than 1° C. and a boiling point of more than 35° C. Ingeneral, however, a wetting liquid has higher reactivity at a highertemperature, and thus, it is preferable in this process that thetemperature of the wetting liquid is higher. For example, if the wettingliquid is an aqueous solution, the liquid temperature under theatmospheric pressure is preferably 35° C. or more, 38° C. or more, 40°C. or more, 42° C. or more, 45° C. or more, 48° C. or more, 50° C. ormore, 52° C. or more, 55° C. or more, 58° C. or more, 60° C. or more,62° C. or more, 65° C. or more, 68° C. or more, 70° C. or more, 72° C.or more, 75° C. or more, 78° C. or more, 80° C. or more, 82° C. or more,85° C. or more, 88° C. or more, 90° C. or more, 92° C. or more, 95° C.or more, or 98° C. or more. Incidentally, the wetting liquid can beheated before and/or during this process.

1-3-4. Separation Process

The “separation process” (S0104) is a process of separating a bagwormsilk thread spun on the surface of the base material from a basematerial after the wetting liquid applying process. It is an essentialprocess in the present invention. The method for separating a bagwormsilk thread from the base material is not limited. The wetting liquidapplying process decreases the bonding force between the base materialand the bagworm silk thread, and thus, both can be separated with arelatively weak tension. For example, the method comprises a method ofholding a bagworm silk thread with the end and ripping off or peelingfrom a base material, a method for jetting air or liquid with highpressure into the bonding surface between a base material and thebagworm silk thread so that the bagworm silk thread can be peeled away,a method for sucking a bagworm silk thread and peeling away from a fixedbase material, a method for immersing a base material in liquid andseparating both with a liquid pressure or the like from the liquid flowcaused by shaking the base material, by stirring the liquid, or thelike. If a liquid is used in this process, the liquid is preferably, butis not limited to, the wetting liquid used in the wetting liquidapplying process. In particular, water is suitable. This process makesit possible to obtain a bagworm foothold silk thread spun on the surfaceof a base material, which was difficult to be collected with aconventional method without damaging the thread.

1-3-5. Washing Process

The “washing process” (S0105) is a process of washing the bagworm silkthread separated in the separation process. This process is an optionalprocess and may be performed if necessary.

The wetting liquid used in the wetting liquid applying process remainson the surface of the bagworm silk thread obtained from the separationprocess. If the wetting liquid used is a solution or a low polarityorganic solvent, and is dried and stuck to the surface of a bagworm silkthread, the bagworm silk thread can be deteriorated or discolored overtime. Therefore, it is preferable that the wetting liquid used iscompletely removed by washing in this process. By this process, part ofthe feces or the like attached to the bagworm silk thread can be removedsimultaneously even when they are present.

A washing solution used for washing in this process is not limited. Ifthe wetting liquid used is a polar liquid, an aqueous solution, or acolloidal solution, a liquid suitable as a washing solution is water(comprising warm water). If the wetting liquid used is a nonpolar liquidsuch as a low polarity organic solvent, another highly volatile solventwith high affinity to the low polarity organic solvent is suitable as awashing solution. For example, when toluene or benzene is used in thewetting liquid applying process, other xylene or ethanol can be used asa washing solution.

The washing method is not limited as long as the wetting liquid used inthe wetting liquid applying process can be removed from the bagworm silkthread. The bagworm silk thread may be sprayed with the washing solutionor immersed in the washing solution.

The number of washes is not limited. The wash can be performed once orplural times. The term “plural times” as used herein refers to, forexample, 2 to 20 times, 2 to 15 times, 2 to 10 times, 2 to 7 times, 2 to5 times, 2 to 4 times, or 2 to 3 times. In general, the wash ispreferably performed plural times. If the wash is performed pluraltimes, the washing solution to be used at each time may be the same ordifferent. Also, the washing methods may be the same or different. Afterthe wash, the thread may be left to be naturally dried, or the washingsolution may be separated and removed by centrifugation using adehydrator or the like.

1-3-6. Scouring Process

The “degumming process” (S0106) is a process of degumming a threadbundle consisting of a bagworm foothold silk thread produced in thisprocess. This process is an optional process and may be performed ifnecessary.

The term “degumming” refers to removing a sericin-like gummy substance(paste-like protein) from the bagworm silk thread to obtain a fibroinfiber.

A method for degumming a bagworm silk thread is not limited inparticular as long as a gummy substance can be removed without weakeningthe strength of the fiber component of the silk thread. For example, anydegumming method for a silkworm silk thread can be applied. In a methodfor degumming a silkworm silk thread, 0.01 mol/L to 0.1 mol/L, 0.03 to0.08 mol/L, or 0.04 to 0.06 mol/L of sodium carbonate solution is usedas a degumming solution, and the solution can be used in the same manneralso in the degumming process in the present method. The obtainedbagworm silk thread may be boiled in the sodium carbonate solution, adegumming solution, for 1 second to 1 hour, 5 seconds to 30 minutes, 10seconds to 15 minutes, 20 seconds to 10 minutes, or 30 seconds to 5minutes.

It is convenient to use a degumming solution such as a sodium carbonatesolution as a wetting liquid used in the wetting liquid applyingprocess, since the same degumming solution is subsequently used in thedegumming process, and a washing process before the degumming process isnot necessary. After being treated in this process, the silk thread maybe washed in the same manner as in the washing process.

After the degumming process, the collected bagworm silk thread may bedried. The drying method is not limited in particular as long as theamount of the wetting liquid, washing solution, or degumming solutionremaining on the bagworm silk thread can be reduced without denaturingor deteriorating the foothold silk thread. For example, the methodcomprises a natural drying method (comprising sun drying) in which thethread is exposed to external air to vaporize the wetting liquid,washing solution, or degumming solution, an air drying method in which ablowing device or the like is used to blow the thread with warm air orcold air; a dehumidification drying method in which a dehumidifyingagent is placed together in a hermetically sealed space for a givenperiod of time, a heat drying method in which the wetting liquid,washing solution, or degumming solution is evaporated and dried byheating; a decompression drying method in which evaporation is performedby degasification with a vacuum pump or the like in a container; orcombinations thereof.

2. Bagworm Silk Thread and Unwoven Fabric Constituted Therewith

2-1. Overview

The second aspect of the present invention is a foothold silk thread ofa bagworm silk thread and an unwoven fabric constituted therewith. Abagworm silk thread and an unwoven fabric according to the presentinvention are obtained using the method for producing a thread bundleaccording to the first aspect.

2-2. Constitution

A thread bundle obtained by the method according to the first aspect isoften in the form of an unwoven fabric in which the bagworm silk threadsare superposed one on another lengthwise and crosswise on the surface ofa base material when the thread bundle is spun on the surface of thebase material without any control of the movement of the bagworm.Accordingly, the bagworm silk thread peeled from the surface of a basematerial in the method for producing a thread bundle according to thefirst aspect can itself be utilized as an unwoven fabric. Furthermore,the foothold silk thread obtained by the method according to the firstaspect can be made into an unwoven fabric by an existing method forproducing an unwoven fabric. Without limitation, a spun lace method or aneedle-punching method can be utilized as an existing method forproducing an unwoven fabric.

Alternatively, when the bagworm silk thread is peeled from the surfaceof a base material with generating a correct end or when the thread isreeled from the correct end pulled off from the state of a peeledunwoven fabric, the thread can be obtained as a long bagworm silkthread.

EXAMPLES Example 1

(Purpose)

A peeling tension evaluation test verifies that the method for producinga thread bundle according to the present invention can easily collect abagworm silk thread (foothold silk thread) spun on a base material,which was difficult to be collected with a conventional method.

(Material)

As a bagworm, a last instar larva of Eumeta japonica (Eumeta japonicabagworm) collected at an orchard in Tsukuba, Ibaraki, Japan was used.Additionally, an acrylic plate, which was approximately 30 cm², was usedas a base material.

(Method)

A sufficient amount of food leaves was fed to a bagworm used in each ofthe Examples until the day before that spinning process was performed.

The bagworm was allowed to spin a thread on the surface of an acrylicplate as a base material by placing the bagworm on the acrylic plateerected vertically and by allowing the bagworm to climb along the wallsurface of the acrylic plate.

After a bagworm silk thread was sufficiently spun on the surface of theacrylic plate, water (pure water), aqueous solutions of 30%, 50%, and70% ethanol, and 99.5% ethanol, a few drops each, were dripped on thesite for evaluation using a syringe. A negative control was a bagwormsilk thread having no wetting liquid applied thereto (a wettingliquid-unapplied sample).

Next, the peeling tension evaluation test used in the present Example isdescribed. As shown in FIG. 2A, the bagworm foothold silk threadpresents a ladder-like zigzag pattern. This foothold silk thread isfixed to the surface of a base material at the turnaround points(referred to as “fixed points”) in a zigzag portion (herein referred toas a “zigzag block”) corresponding to the steps of a ladder shown in thebroken line ellipse in FIG. 2A. When the foothold silk thread is beingpeeled away, the tension exhibits a peak at a fixed point in each zigzagblock because the largest force is needed at the fixed point, but oncebeing peeled, the tension is relaxed down to the initial value of zerobecause the foothold silk thread is not fixed to the base material tothe next fixed point. At this next fixed point, a large tension isneeded in the same manner when the thread is peeled away, but thetension becomes the initial value immediately after the peeling. Whenthe foothold silk thread is being peeled away, this cycle is repeatedbetween every zigzag block. In the peeling tension evaluation test, oneend of a bagworm foothold silk thread spun on the surface of a basematerial is fixed to a load cell of a tensile tester, and then, thebagworm silk thread is peeled off at a constant speed, with variationsin the tension being continuously recorded, thus the process ofreleasing the adhesion at the fixed points to sequentially unbend thezigzag foothold thread into a linear form can be measured as therelationship between a peeled length (pulled off distance) and atension.

Each wetting liquid was applied to a bagworm silk thread and thesufficient wetting of which was verified, and then, one end of thebagworm silk thread on each acrylic plate was pulled off and fixed tothe load cell of the tensile tester. The fixed bagworm silk thread waspeeled off at a constant speed (100 μm/sec), with variations in thetension being continuously recorded on the load cell. This measurementwas made using a tensile tester (a small tabletop tester, EZ Test, fromShimadzu Corporation).

In this Example, the total of peak areas per zigzag block obtained inthe peeling test was divided by the peeled length to calculate a peelingenergy per unit peeled length. In order to minimize the influence ofdifferences between bagworm individuals used in the spinning process onthe adhesive force, the result obtained from when each wetting liquidwas used was normalized with the peeling energy of a negative control(wetting liquid unapplied sample), in which a foothold silk thread isspun by the same bagworm individual, and was evaluated and compared inpercentage (%) assuming that the peeling energy for the negative controlwas 100.

(Result)

The results are shown in FIG. 4 and Table 1.

TABLE 1 EtOH Concentration H₂O 30% 50% 70% 99.5% Relative value (%) 2911 7 10 6

In FIG. 4, the horizontal axis indicates the peeled length (mm), and thevertical axis indicates the peel tension (N). As shown in FIG. 4(A), thenegative control required a relatively strong peeling tension of 0.003to 0.004 N at each fixed point per zigzag block. In contrast, in thecase where water was applied, the peeling tension was approximately0.001 N, showing a decrease to approximately ¼ of that for the negativecontrol, as shown in FIG. 4(B). Furthermore, when ethanol (99.5%) wasapplied, it was revealed, as shown in FIG. 4(C), that the peelingtension was 0.0001 to 0.0002 N, showing a dramatic decrease toapproximately 1/20 to 1/40 of that for the negative control.

As shown in Table 1, the peeling energy was decreased to approximately30% of that for the negative control when water was applied to a basematerial and a bagworm silk thread. When ethanol (99.5%) was applied,the peeling energy was decreased to 6% of that for the negative control,exhibiting a more marked effect than water. This effect of ethanol wasalso maintained at various concentrations when an aqueous ethanolsolution, a solution mixture of ethanol and water, was used. At any ofthe concentrations, the effect was verified as higher than that ofwater.

Example 2

(Purpose)

A peeling tension evaluation test verifies that the method for producinga thread bundle according to the present invention can be used with theother wetting liquid other than water and ethanol.

(Method)

The basic procedures and basic operation were performed as in Example 1.The wetting liquids used here were: methanol (MeOH) as a polaritymonovalent alcohol; 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) as apolarity halogen-containing organic solvent; dimethylsulfoxide (DMSO) asa polarity sulfur-containing organic solvent; carbon tetrachloride as alow polarity halogen-containing organic solvent; glycerin as a polaritytrivalent alcohol; furthermore, an aqueous solution of sodium chloridehaving a concentration of 0.05 M (NaCl aq); and an aqueous solution of0.05 M sodium carbonate (Na₂CO₃ aq) widely used in a degumming processfor a silkworm silk thread.

(Result)

The results are shown Table 2.

TABLE 2 Carbon 0.05M 0.05M MeOH HFIP DMSO Tetrachloride Glycerin Na₂CO₃NaCl Relative value (%) 11 13 13 6 14 6 11

As shown in Table 2, with any wetting liquid, the peeling energy wasdecreased to 15% or less of that for the negative control. Additionally,a high effect was verified with any of the liquids, showing that half orless of the peeling energy for the water-applied sample was sufficient.

All publications, patents, and patent applications cited herein shouldbe incorporated herein by reference in their entirety.

1. A method for producing a thread bundle of a bagworm silk thread,comprising: wetting liquid applying process of applying a wetting liquidto the bagworm silk thread spun on the surface of a base material; andseparating the bagworm silk thread from the base material, wherein thewetting liquid is in a liquid form at least in the range of 20° C. ormore and less than 30° C. under the atmospheric pressure, and is a puresubstance or a mixture that does not damage, denature, or dissolve afibroin protein which is a fiber component of the bagworm silk thread.2. The method according to claim 1, further comprising a spinningprocess of placing a bagworm on the surface of the base material beforethe wetting liquid applying process and allowing the bagworm to spin thethread.
 3. The method according to claim 2, further comprising a bagwormcollection process of collecting the bagworm together with a nest afterthe spinning process and before the wetting liquid applying process. 4.The method according to claim 1, further comprising a washing process ofwashing the separated bagworm silk thread.
 5. The method according toclaim 1, further comprising a degumming process of degumming theseparated bagworm silk thread.
 6. The method according to claim 1,wherein the wetting liquid is a pure substance or a mixture that has amelting point of less than 20° C. and a boiling point of 30° C. or moreand 300° C. or less.
 7. The method according to claim 1, wherein thewetting liquid is an aqueous solution or an organic solvent.
 8. A methodfor collecting a bagworm silk thread spun on the surface of a basematerial, comprising: applying a wetting liquid to the bagworm silkthread spun on the surface of the base material; and separating thebagworm silk thread from the base material, wherein the wetting liquidis in a liquid form at least in the range of 20° C. or more and lessthan 30° C. under the atmospheric pressure, and is a pure substance or amixture that does not damage, denature, or dissolve a fibroin proteinwhich is a fiber component of the bagworm silk thread.
 9. The methodaccording to claim 8, wherein the wetting liquid is an aqueous solutionor an organic solvent.
 10. A bagworm silk thread(s) obtainable by themethod according to claim
 1. 11. An unwoven fabric formed of a bagwormsilk thread(s) obtainable by using the method for producing a threadbundle according to claim
 1. 12. A bagworm silk thread(s) obtainable bythe method for collecting a bagworm silk thread according to claim 8.